2 METER FM
RECEIVER KIT
Ramsey Electronics Model No. FR146
Keep an ear on the local repeater action from your easy chair
with this simple and fun to build FM receiver. Tune the entire 2
Meter band or the VHF high Police and Fire band.
• Tunes any 5 MHz portion of the 136 to 175 MHz band.
• Excellent performance, less than 1 uV sensitivity.
• Tuned input, low noise preamp stage.
• True Dual-conversion superhet design with 2 pole
Ceramic High IF and 6 pole Ceramic low IF filters!
• Front Panel Volume, Squelch, and Tuning controls.
• Excellent receiver for weather band, police, fire, etc.
• Informative manual answers questions on theory, hook-
ups, and uses - enhances resale value, too!
• Add our case set for a finished ‘Pro’ look. Cases match
all Ramsey products.
• Clear, concise assembly instruction carefully guides
you to a finished kit that works the FIRST time!
FR146 • 2
PARTIAL LIST OF AVAILABLE KITS
RAMSEY TRANSMITTER KITS
• FM10A FM Stereo Transmitter
• FM100B Professional FM Transmitter
• FM25B Synthesized FM Stereo Transmitter
• AM25 Synthesized AM Transmitter
• AM1 AM Transmitter
RAMSEY RECEIVER KITS
• FR1 FM Broadcast Receiver
• AR1 Aircraft Band Receiver
• AA7 Active Antenna
• SC1 Shortwave Converter
RAMSEY HOBBY KITS
• SG7 Personal Speed Radar
• SS70 Speech Scrambler
• TT1 Telephone Recorder
• PG13 Plasma Generator
• MD3 Microwave Motion Detector
• TFM3 Tri-Field Meter
• WEB1 Walking Electronic Bug
RAMSEY AMATEUR RADIO KITS
• HR Series HF All Mode Receivers
• QRP Series HF CW Transmitters
• DDF1 Doppler Direction Finder
• CPO3 Code Practice Oscillator
• QRP Power Amplifiers
RAMSEY MINI-KITS
Many other kits are available for hobby, school, scouts and just plain FUN. New
kits are always under development. Write or call for our free Ramsey catalog.
FR146 2 METER FM RECEIVER KIT INSTRUCTION MANUAL
Ramsey Electronics publication NO. MFR146 Rev. E1
First printing: January 1992
COPYRIGHT 1992 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York
14564. All rights reserved. No portion of this publication may be copied or duplicated without the
written permission of Ramsey Electronics, Inc. Printed in the United States of America.
FR146 • 3
FR146 2 METER
FM RECEIVER KIT
Ramsey Publication No. MFR146
Price $5.00
TABLE OF CONTENTS
I
ntroduction to the FR146 .............. 4
Circuit Description ......................... 5
Parts List ........................................ 6
Simplified Block Diagram .............. 8
Parts Layout Diagram .................... 9
FR146 Assembly Instructions ........ 10
Schematic Diagram ....................... 12
Testing and Alignment ................... 18
Enclosure Ideas ............................. 20
Troubleshooting Guide .................. 21
Notes for Advanced Users ............ 21
Ramsey Kit Warranty ..................... 23
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
FR146 • 4
INTRODUCTION TO THE FR146 FM RECEIVER
Most Ramsey kits can be classified as “Skill Level 1”. That means that our
kits are intended to be sucessful for first-time kit builders. This FR146 FM
Receiver is best regarded as a “Skill Level 2” project (or at least Level 1.46!)
and should not be taken lightly, even by experienced, licensed radio
amateurs.
Still, this step-by-step manual is written with the beginner in mind, because
we are well aware of the fascination that Two Meters and its maze of
repeaters holds for newcomers, which means this could be your very first kit
project. The same holds true for those who just want to peek in on VHF
public service communications without the cost of a scanner. To be honest,
we'd like to see first-time builders start out with an easier kit such as the
Ramsey HR-40 Forty Meter receiver before assembling the FR146, but we
are confident that you can construct the FR146 successfully if you follow this
manual carefully and patiently.
This receiver is a good project for amateurs wishing to become more familiar
with 2 meter FM before choosing a transceiver, or for those active on 2 who
want an inexpensive receiver to take on trips, keep in a briefcase or to watch
for band openings.
Before beginning the project or even studying the circuit description, it is
worthwhile to develop some prior respect for how much receiver is packed
onto the circuit board. The nine semiconductor devices (diodes, transistors
and IC chips) give the equivalent of about 30 or more transistors diodes.
And, in addition to four inductors, a crystal and two ceramic filters, there are
nearly 60 capacitors and resistors. Surely, all that should result in a decent
receiver! You could easily spend twice the money plus hours of time trying to
gather the equivalent parts from catalogs and still need to make your own
circuit board.
BUILDING YOUR FR146 KIT
There are just over 200 solder connections on the FR146 printed circuit
board. That means your work could be 99% excellent and you could STILL
have 2 or 3 cold solder points or solder bridges. Since this circuit is more
sophisticated than a direct-conversion HF receiver or a simple transmitter, a
beginner or casual amateur could have a harder time tracing a problem due
to a poor solder connection. Therefore, PLEASE take us seriously when we
say that good soldering is essential to the proper operation of your receiver!
Use a 25-watt soldering pencil with a clean, sharp tip.
Use only rosin-core solder intended for electronics use.
FR146 • 5
Use bright lighting. A magnifying lamp or bench-style magnifier may be
helpful.
Do your work in stages, taking breaks to check your work.
Carefully brush away wire cuttings so they don't lodge between solder
connections.
FR146 CIRCUIT DESCRIPTION
VHF signals from the antenna are amplified through the tuned input circuit (L1,
C3 and L2,C4) by Q1, a microwave bipolar transistor. Q1's output is fed to the
input of the SA602 IC, an efficient single-package (8-pin DIP) mixer-product
detector-oscillator. The tuneable oscillator section of the SA602 is aligned to
operate at 10.7 MHz higher than the signal fed and amplified by Q1. For
example, to receive 144-148 MHz signals, the oscillator must tune 154.7 to
158.7 MHz in order for the SA602's mixing capability to produce a steady 10.7
MHz output signal to the rest of the circuit. The oscillator frequency is
determined by L3 and its associated capacitors, and varied by the varactor
tuning network using D1 and varied by R1.
The output from pin 4 of the SA602 passes through a ceramic 10.7 MHz filter,
amplified by transistor Q2 and applied to input pin 18 of U2.
Q3 provides AFC (Automatic Frequency Control) by keeping the local oscillator
of U1 from drifting away from an incoming signal. This is accomplished by
tuning the varactor circuit in the direction opposite the drift.
The MC3359 IC has an internal oscillator controlled by the 10.24 MHz crystal.
The 10.24 MHz signal is mixed with the 10.7 MHz input from U1 to convert
down to the low IF of 450 KHz. The 450 KHz IF is filtered by FL2 and then
amplified by a limiting amplifier in U2. Audio demodulation takes place in the
quadrature detector, with L4 adjusting the detector.
The audio modulation is detected in U2, and the background noise is used to
control the squelch. U3 amplifies the audio output from pin 10 of U2 to a
practical level for speaker or headphone operation. Pin 16 of U2 will ground the
input of U3 when the squelch is closed.
L4, a 450 KHz IF coil, permits adjustment of the 90-degree voltage-current
phasing ("quadrature") of FL2's output to the FM detector demodulator (pin 8 of
the MC3359).
FR146 • 6
PARTS LIST
Inductors
2 small 1 1/2 turn coils (L1,L2)
1 slug-tuned 3 1/2 turn coil [orange color] (L3)
1 shielded transformer coil [marked LB 53303] (L4)
Semiconductors and IC's
1 2SC2498 or 2SC2570A transistor (Q1)
3 2N3904 transistor (Q2,Q3,Q4)
1 SA602 8-pin IC (U1)
1 MC3359 18-pin FM receiver IC (U2)
1 LM386 8-pin audio amplifier IC (U3)
1 Varactor diode, BB505 [orange body marked BB505] (D1)
1 1N4148 signal diode (D2)
Special Components
1 10.24 MHz Crystal (Y1)
1 10.7 MHz ceramic filter [brown, molded, 3 leads] (FL1)
1 450 KHz ceramic filter [black, square] (FL2)
Fixed Resistors
1 2 ohm [red-black-gold] (R22)
3 270 ohm [red-violet-brown] (R6,9,20)
1 470 ohm [yellow-violet-brown] (R5)
2 1K ohm [brown-black-red] (R11,12)
3 10K ohm [brown-black-orange] (R7,17,19)
1 18K ohm [brown-gray-orange] (R18)
1 33K ohm [orange-orange-orange] (R14)
4 47K ohm [yellow-violet-orange] (R4,8,13,21)
1 100K ohm [brown-black-yellow] (R16)
1 470K ohm [yellow-violet-yellow] (R15)
1 1 megohm [brown-black-green] (R10)
Capacitors
1 8.2 pF (C12)
2 10 pF (C2,5)
2 15 pF (C9,10)
1 22 pF (C19)
2 56 pF (C3,4)
3 100 pF [marked 100, 101, or 101K] (C1,6,22)
1 220 pF [marked 220 or 221] (C18)
7 .001 uF [marked .001 or 102 or 1 nF] (C7,8,11,20,23,24,25)
8 .01 uF [marked .01 or 103 or 10 nF] (C13,16,17,21,26,28,29,31)
1 .1 uF [marked .1 or 104] (C34)
1 1.0 uF electrolytic (C27)
FR146 • 7
3 4.7 or 10 uF electrolytic (C15,30,36)
4 100 to 220 uF electrolytic (C14,32,33,35)
Controls and Hardware
1 Printed circuit board
3 10K ohm potentiometer (R1,R2,R3)
1 DPDT push switch (S1)
1 PC mount RCA jack (J1)
1 PC mount subminiature speaker jack (J2)
1 9-volt battery bracket
1 9-volt battery snap-on clip
REQUIRED, NOT SUPPLIED
1 9-volt alkaline battery
1 VHF antenna with cable terminated in RCA-style plug or adapter
1 Speaker or headphones
NOTE CONCERNING THE AUDIO OUTPUT JACK
Your receiver kit is supplied with a standard subminiature 2.5 mm (3/32") audio
output jack, which mates with commonly available earphone plugs and
adapters available at Radio Shack, such as 274-290 (plug) or 274-327 (adapter
for 1/8" mono plug). If you prefer to use another size and style jack, we suggest
that you still install the original jack and then wire your own jack in parallel with
it rather to rough up the PC board to accommodate your jack.
SEMICONDUCTOR REPLACEMENT DATA
U1 SA602 (Signetics) Contact Ramsey Factory
U2 MC3359 (Motorola) ECG860 or SK7731
U3 LM386 (National) available at Radio Shack, other suppliers
Q1 2SC2498 ECG10 or SK9139
Q2,3 2N3904 available at Radio Shack, other suppliers
D1 BB505 contact Ramsey Factory
D2 1N4148 available at Radio Shack, other suppliers
FR146 • 8
U2, 3359
FR146 BLOCK DIAGRAM
U1
SA602
MIXER
FR146 • 9
FR146 PARTS LAYOUT DIAGRAM
FR146 • 10
RAMSEY “Learn-As-You-Build” KIT ASSEMBLY:
We have a twofold "strategy" for the order of the following kit assembly steps.
First, we install parts in physical relationship to each other, so there's minimal
chance of inserting wires into wrong holes. Second, whenever possible, we
install in an order that fits our "Learn-As-You Build" Kit building philosophy.
FOR EACH PART, OUR WORD "INSTALL" ALWAYS MEANS THESE STEPS:
1. Pick the CORRECT part value to start with.
2. Insert it into the CORRECT PC board location.
3. ORIENT it correctly, which means: PLEASE follow the PC board drawing
and the written directions for ALL parts where there's a right way AND a wrong
way to solder it in. (Diode bands, electrolytic capacitor polarity, transistor
shapes, dotted or notched ends of IC's, and so forth.)
4. Solder ALL connections unless directed otherwise. Use enough heat and
solder flow for clean, shiny, completed connections. Don't be afraid of ANY
pencil style soldering iron having enough heat to damage a component.
5. Trim or "nip" excess wire lengths after soldering.
NOTE: Save some of the longer wire scraps nipped from resistors and
capacitors. These will be used to form wire jumpers (JMP1, etc.) to be soldered
in just like parts during these construction steps.
Now, let's start building!
❒ 1. Press S1 firmly into its six holes and solder all six pins. The switch fits
the board only one way.
❒ 2. Install J1, the RCA-style antenna jack. Solder all 4 points.
❒ 3. Install J2, the subminiature phone jack. Solder all three points. Be
gentle and patient in inserting, so as not to damage the solder tabs.
❒ 4. Install controls R1, R2 and R3. Insert the three PC mounted controls
into their positions. Check that the controls are pressed in firmly and
straight against the top of the board. Solder the three center pins and then
the two larger mechanical mounting tabs. Use enough solder for a solid
connection.
Also, if you plan to use an enclosure other than the custom Ramsey enclosure
and knob kit, you may wish to locate the controls differently than provided by
the PC board. In this case, the control lugs are wired to the PC board using
your own insulated hookup wire, kept as short as possible for neat installation.
FR146 • 11
FURTHER COMPONENT INSTALLATION
All "directions" on the PC board (ie: right, left, above, below and so forth)
assume orientation of your board as shown in the parts layout diagram.
Therefore the rear of the board (connectors) is the lower end, and the front
(controls) is the upper end.
1. ANTENNA INPUT AND TUNED RF PREAMPLIFIER
❒ 5. Install C1, 100 pF disc capacitor.
❒ 6. Install C2, 10 pF.
❒ 7. Install C3, 56 pF.
❒ 8. Install L1, one of the small 1 1/2 turn coils.
❒ 9. Install C4, 56 pF.
❒ 10. Install L2, just like L1 above.
❒ 11. Install C5, 10 pF.
❒ 12. Clearly identify Q1, the 2SC2498 or 2SC2570A transistor. Do not
confuse it with the other transistors supplied. Position Q1 as shown on the
PC board layout, with the flat side facing to the right, toward the middle of
the board. Press the transistor snugly into the PC board so that only a
minimum amount of wire lead is exposed above the board. In soldering,
don't be afraid to use enough heat to make good clean connections.
❒ 13. Install R4, 47K. [yellow-violet-orange] just to the left of Q1.
❒ 14. Install C6, 100 pF. [marked 100, 101, or 101K]
❒ 15. Install R5, 470 ohms. [yellow-violet-brown]
2. SA602 OSCILLATOR-MIXER and VARACTOR TUNING
❒ 16. Install R6, 270 ohms. [red-violet-brown]
❒ 17. Install C7, a .001 uF bypass capacitor. [marked .001, 102, or 1 nF]
❒ 18. In installing the SA602 IC, you may wish to use an 8-pin DIP socket
rather than soldering the IC directly to the board. Reasons for doing this
might include the peace of mind of beginners afraid of damaging the IC, or
experienced builders testing the merits of the SA602's cousin, the SE602.
However, please be aware that we have seen more service problems with
improper socket insertion than from soldering heat damage to IC's. Even if
this is your first IC, don't be afraid to use enough heat to make 8 clean
connections, but DO be sure to correctly orient the end marked by a band,
FR146 • 12
FR146 • 13
FR146 • 14
dot, or notch. Before soldering, make sure that the IC or socket is perfectly
fflat against the top of the PC board. Install U1, the SA602, in accord with
the preceding directions.
❒ 19. Install FL1, the ceramic filter. This component looks like a capacitor
with 3 leads and may be installed either way.
❒ 20. Install jumper wire JMP4. Use a scrap component lead wire bent like a
staple that connects the two PC board holes. Jumpers act as "bridges" over
PC board traces underneath.
❒ 21. Install C8, .001 uF [marked .001, 102, or 1 nF].
❒ 22. Install C10, 15 pF.
❒ 23. Install R7, 10K. [brown-black-orange].
❒ 24. Install C9, 15 pF.
❒ 25. Install C11, .001 pF [marked .001,102, or 1 nF].
❒ 26. Install L3, the slug tuned coil. It is important that the body of this coil be
snug against the PC board for mechanical stability, which directly affects
the frequency stability of the receiver. Make good, solid solder connections!
❒ 27. Install C12, 8.2 pF.
❒ 28. Install varactor diode D1, marked BB505. It is important to orient this
part as shown in the parts layout diagram.
❒ 29. Install R8, 47K ohms [yellow-violet-orange].
❒ 30. Install R9, 270 ohms [red-violet-brown].
❒ 31. Install C13, .01 uF (marked .01 or 103 or 10 nF).
C14 is the first of the electrolytic or "polarized" capacitors that you will install.
This means these capacitors have a positive (+) and negative (-) side and
therefore a right and wrong way to be installed. Ordinarily, only the negative
side is marked on the capacitor; a dark band with the (-) sign clearly shown.
The value of C14 is not critical and may be any value from 100 to 220uF.
❒ 32. Install C14, 100 to 220 uF, observing correct polarity.
❒ 33. Install C15, 4.7 or 10 uF, observing correct polarity.
❒ 34. Install jumper JMP1.
❒ 35. Install jumper JMP3.
FR146 • 15
PROGRESS SUMMARY
So far, you have wired the tuned input from the antenna, the RF preamplifier,
and the SA602 mixer-oscillator, including the varactor tuning circuit. The work
you have done has actually formed a simple receiver capable of tuning in VHF
signals of all kinds and converting them to a low-level 10.7 MHz output to be
amplified by Q2. This is a good time to review the steps completed to this
point before proceeding. Due to the many functions of the MC3359 FM
receiver IC, further assembly steps will be in the order of easiest parts
installation.
3. TRANSISTOR COUPLING & AFC CIRCUITS, VOLUME & SQUELCH
CONTROLS
❒ 36. Install Q2, a 2N3904 transistor. Correctly position the flat side.
❒ 37. Install R13, 47K ohms (yellow-violet-orange).
❒ 38. Install C20, .001 uf (marked .001 or 102).
❒ 39. Install R12, 1K ohms (brown-black-red).
❒ 40. Install Q3, 2N3904 transistor.
❒ 41. Install R10, 1 megohm (brown-black-green).
❒ 42. Install R11, 1K ohms (brown-black-red).
❒ 43. Install R22, 2 ohms (red-black-gold).
❒ 44. Install C29, .01 uf (marked .01 or 103 or 10nf).
❒ 45. Install C30, 10 uf electrolytic, observe correct polarity.
❒ 46. Install R18, 18K ohms. (brown-gray-orange).
❒ 47. Install C28, .01 uf (marked .01, 103, or 10nf).
❒ 48. Install R19, 10k ohms (brown-black-orange).
❒ 49. Install jumper wire, JMP2.
❒ 50. Install C34, .1 uf (marked .1 or 104).
❒ 51. Install R21, 47K ohms (yellow-violet-orange).
❒ 52. Install C35, 100 to 220 uf electrolytic, observe polarity.
❒ 53. Install R20, 270 ohms (red violet-brown).
❒ 54. Install Q4, 2N3904 transistor.
FR146 • 16
4. MC3359 FM IC and ASSOCIATED COMPONENTS
❒ 55. Install R17, 10K ohms [brown-black-orange]
❒ 56. Install R14, 33K ohms [orange-orange-orange]
❒ 57. Install C24, .001 uF [marked .001, 102, or 1 nF].
❒ 58. Install C25, .001 uF [marked .001, 102, or 1 nF].
❒ 59. Install C26, .01 uF [marked .01, 103, 10 nF].
❒ 60. Install L4, the 455 KHz quadrature coil [marked LB53303], soldering
the two pins and the two mounting tabs.
❒ 61. Install MC3359 IC, U2. As in the case of the SA602 IC, you could
choose to install an 18-pin IC socket rather than soldering the IC directly.
Re-read the discussion of IC sockets offered for the installation of U1.
Larger IC's such as the MC3359 require considerably more care in socket
insertion. Notice that the end of the IC marked by a band, dot, or notch
must be oriented correctly as shown on the parts layout diagram. Solder
each of the 18 connections carefully. Make sure you have good lighting as
well as good technique to make sure that no solder "bridges" flow
between the connections.
❒ 62. Install C22, 100 pF (marked 100, 101, or 101K).
❒ 63. Install C16, .01 uF [marked .01 or 103 or 10 nF].
❒ 64. Install C17, .01 uF [marked .01 or 103 or 10 nF].
❒ 65. Install C21, .01 uF [marked .01 or 103 or 10 nF].
❒ 66. Install C18, 220 pF [marked 220 or 221].
❒ 67. Install C19, 22 pF.
❒ 68. Install Y1, the 10.24 MHz. crystal. No special procedure is required.
Simply press the crystal firmly into its holes as far as it will go, and make
good solder connections.
❒ 69. Install FL2, the 450 KHz filter. Its three leads are delicate and fit in
only one way.
❒ 70. Install C23, .001 uF [marked .001, 102, or 1 nF].
❒ 71. Install C27, 1 uF electrolytic, observe correct polarity.
❒ 72. Install D2, the 1N4148 signal diode, observe correct orientation of the
banded cathode end. Be sure you correctly identified D2 and did not
confuse it with the varactor diode already installed.
FR146 • 17
❒ 73. Install R16, 100K ohms [brown-black-yellow].
❒ 74. Install R15, 470K ohms [yellow-violet-yellow].
5. FINAL CONNECTIONS: THE LM386 AUDIO IC STAGE
You now have a working FM receiver ready for adjustment. The output of the
MC3359 FM IC simply needs to be boosted to listening level. A few more
connections, and your receiver will be ready for adjustment and testing! Now
would be a good time to review some of your previous work and also to make
sure you have on hand what you'll need for testing: antenna, fresh battery,
earphone or speaker with correct plug or adapter.
❒ 75. Review the instructions for installing U1 and U2. Insert the LM386 IC
(U3) with the band or dot oriented correctly. Solder the 8 connections.
❒ 76. Install C32, a 100 to 220 uF electrolytic, observe correct polarity.
❒ 77. Install C31, .01 uF (marked .01, 103, or 10 nF).
❒ 78. Install C36, 4.7 or 10 uF electrolytic, observe polarity.
❒ 79. Install C33, 100 to 220 uF electrolytic, observe polarity.
❒ 80. Install the battery snap terminal in the two holes below S1, making
sure that the positive (red) lead is inserted into the (+) hole on the PC
board.
❒ 81. The battery bracket may be attached in a variety of ways. A wire
jumper can be passed through the two holes on the PC board, then both
ends soldered on the underside of the board. You may prefer to use very
small screws or even a double-sided mounting adhesive strip or glue. In
using such methods, make sure that the battery will not block the PC
board's mounting hole in its vicinity.
Wiring of the PC board is now complete. If you have the patience, we suggest
a short break. Then take a magnifying lens and a bright light and examine all
your solder joints, touching up any connection which appears less than
perfect. Make sure all excess leads have been trimmed, and that one is not
bent back flat against the board, possibly causing a short. Brush the solder
side of the board with a stiff brush to make sure that no loose wire trimmings
or solder drippings (tsk tsk) are lodged between connections.
FR146 • 18
TESTING, ALIGNMENT AND ADJUSTMENT
To prepare the FR146 FM VHF Receiver for reliable monitoring operation, you
will need these basic tools:
❒ 1. A useful VHF signal source.
❒ 2. Hexagonal, non-metallic coil slug alignment tool for L3.
❒ 3. Small screwdriver to adjust L4.
1. Signal source:
This signal can be from your test bench equipment or from a
"live" source such as a local repeater. The "live" signals are best for fine-tuning,
but they also have that VHF communications character of being fast and to the
point. Good test bench signal sources include your own 2-meter tranceiver, if
you are licensed to use it, a signal generator or grid-dip oscillator. If you do not
have a steady test signal source for the band within 135-175 MHz of primary
interest to you, and still wish to verify immediately the proper operation of your
FR146, a good and steady VHF signal source will be your local NOAA Weather
Service station, broadcasting around 160 MHz. Once you have verified reliable
reception of your regional NOAA station, adjustment to your desired listening
range will become easier.
2. L3 Alignment Tool:
If you do not already have a set of plastic or nylon coil
alignment tools and do expect to try further Ham radio or electronic hobby
projects, such tools are worth having and can be found inexpensively at any
electronics store including Radio Shack. While a metal Hex key wrench can fit
the coil slug, the metal itself would damage the coil inductance drastically and
therefore should not be used. With patience and sandpaper, a useable tool
might be formed from a wood or plastic rod.
ALIGNMENT PROCEDURE
❒ 1. Make sure the power switch is off.
❒ 2. Connect the antenna, earphone or speaker and battery.
❒ 3. Turn the slug of L3 until it is even with the top of the coil form.
❒ 4. Now, turn the slug of L3 clockwise 7 turns back into the form.
❒ 5. Turn the slug of L4 until it is flush with the top of the coil and then turn it 2
turns back into the coil.
❒ 6. Turn all three controls to the left, fully counterclockwise.
❒ 7. Turn the power ON.
❒ 8. Turn R2 (Volume control) until you hear some noise.
❒ 9. Adjust L4 for maximum noise from the speaker.
FR146 • 19
Further alignment now consists of adjusting the oscillator coil L3 to permit the
tuning control (R1) to cover the 5 MHz. segment between 135 and 175 MHz of
primary interest to you. Assuming you wish to adjust for the Two Meter 144-148
MHz Amateur Band, adjust L3 until you hear your intended test signal.
If you are a beginner with no license or other equipment, any Ham operator with
a 2-meter transceiver should be willing to give you the test signal and extra help
that you need. The FR146 is very sensitive, so operate the transceiver on low
power on a simplex frequency from a distance of at least across the room. An 8"
piece of wire will be a sufficient receiving antenna for such tests. If you don't
know any Hams, visit a friendly two-way radio service center to get close to the
test signal you need!
RECEIVER SENSITIVITY
Your FM receiver features sensitivity under 1 uv. Radio Hams constantly marvel
at how an FR146 displayed at hamfests tunes in dozens of hand-held QSO's on
the premises without an antenna connected! You can expect to monitor local
repeater and simplex transmissions easily, using a simple groundplane style
antenna. The receiver also responds very well to the addition of a low-noise pre-
amplifier such as the Ramsey SA-7/PR-2. For 2 meters, the Ramsey PR-10,
with its high-Q tuned circuitry and exceptional signal-to-noise ratio, offers
significant performance improvement. A new and versatile receiver accessory is
the Ramsey AA-7 HF-VHF Active Antenna, which doubles as a preamplifier with
other antennas in addition to the excellent performance of its own whip.
ADDING AN LED POWER "ON" INDICATOR
For many people, a pilot lamp to indicate "power on" is more than a nice touch.
They expect it and depend on it, reminding us that "real radios glow in the dark!"
Adding a simple LED power-on indicator to your Ramsey kit receiver is easy. All
you need is the LED itself and a small 1K to 2.2K resistor.
Study the PC traces between the positive battery supply wire and the on-off
switch. The unused connectors on top of your switch are an ideal point to get the
+ DC voltage needed for the anode (longer lead) of the LED. Plan where and
how you wish to install the LED in your enclosure.
FR146 • 20
Locating the LED immediately above the on-off switch is logical and ideal. The
simplest way to make a good installation is to drill a neat hole just slightly
smaller than the diameter of the LED. Then, enlarge the hole a little bit at a time
just enough to let the LED be pressed in and held firmly. The resistor may be
connected to either the anode or cathode of the LED, but the anode MUST go
to + DC, with the cathode connected to the nearest common ground point. If
you are wondering why we did not include these pennies worth of parts with
your kit, you can believe any of the following reasons:
(1) We wanted to stretch your battery budget: with the LED drawing about 6
ma, how long will your battery last if you leave your receiver on for a few days,
just like we leave our computers and Ham or computer accessories on all the
time?
(2) We thought you'd have more fun planning and installing your own lamp that
glows in the dark!
(3) We could not decide which color you would like best!
THE RAMSEY ELECTRONICS CASE, KNOB & HARDWARE
OPTION
Your finished receiver can be installed in a variety of enclosures of your own
design and choosing. You might be planning to combine several Ramsey circuit
boards in a single enclosure. Use of the inexpensive and attractive Ramsey
case and knob kit will give your unit that finished look and increase its resale
value. These sturdy black instrument cases are supplied with front and rear
panels, panel stickers, knobs, rubber feet and mounting screws.
OTHER ENCLOSURE RECOMMENDATIONS
While we believe that the Ramsey enclosure and knob option is a fine value for
finishing off your Ramsey receiver or transmitter, we are happy to give you a
couple of additional suggestions. If your first goal is economy and rugged
portability, you will find that the circuit board can be mounted nicely in a
standard VHS videotape storage box, which also gives room for a speaker, or
earphone storage, and even a roll of antenna wire. The controls are easily
mounted at one end of such a box. It may be necessary to cut away the molded
posts which secure the tape cassette itself. These storage boxes come in
several styles, so pick one that looks truly practical as a project enclosure.
To accomplish RF shielding, the most economical metal enclosure nicely suited
for Ramsey amateur kit boards is Radio Shack No. 270-253A. This metal utility
cabinet can accommodate both a receiver and transmitter board, plus speaker,
with room for various refinements you might like to add.
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